The purpose of this project is to examine the subcellular and extracellular structure of nerve and muscle and relate such structure to function. Electron microscopy, protein chemistry, structural modeling, physical chemistry and electrophysiological methods are employed. The following structures are probed: 1) Cytoskeleton, 2) Neurofilaments, 3) microtubules, 4) Schwann sheath, 5) Schwann cells, 6) Endoneurium. The Schwann sheath and generalized neuronal packing are modeled. In addition, the ionic composition of squid hemolymph is examined. BIBLIOGRAPHIC REFERENCES: Adelman, W.J., Moses, J. and Rice, R. V.: An anatomical basis for the resistance and capacitance in series with the excitable membrane of the squid giant axon. J. Neurocytology (in press), 1977. Shoukimas, J., Adelman, W.J. Jr. and Sege, V.: Cation concentrations in the hemolymph of Loligo pealei. Biophysical J. 18: 231-234, 1977.